233009037-ns2-network-simulator-tutorial-for-begineers.pdf 6j5e4c

Ns2 Network Simulator Tutorial for Beginners’

Udhay Prakash Udhayprakash.blogspot.in Uday3prakash @gmail.com

Presentation Agenda • Introduction to Linux • Importance of Open Source software • Network Simulators • Importance and usage of ns2 • Ns2 Installation • TCL scripting language • Introduction to NAM and Xgraph • Discussion about trace file format

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Outcomes • To get ease with Linux platform • Open Source vs Free ware vs proprietary • To insight about a Network Simulator •

Importance of ns2 network simulator

• Scripting language vs programming language • Ability to install ns2, nam and xgraph • Ease in working with TCL scripting • Insight to NAM and Trace files

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SESSION -1 Introducing to Linux and Ns2

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Linux • Developed under GNU project. • Open Source software, except RedHat • Major Linux Families » Debian, Ubuntu, Mint, …. » Fedora » OpenSUSE » ArchLinux » CentOS & RedHat

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Working in Linux • Are you new to Linux Operating System? • Are you more habituated to Windows or Macintosh Operating Systems ? • Then, carefully follow me… (switch on your PCs) – Creating a file – Reading/writing/editing a file – Operating System specific file types

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Why Simulators? • Advantages ☺Complex scenarios can be easily tested ☺Cheap-does not require costly equipment ☺Results can be quickly obtained-more ideas can be tested in a smaller timeframe ☺Controlled experimental conditions ☺Repeatability helps aid debugging

• Disadvantages ☻Not real ☻Real systems too complex to model ☻Consideration of practical conditions 04-Jul-14

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NS2 Network Simulator • Open-source event-driven simulator • Designed specifically for research in computer communication networks. • Contains modules for numerous network components such as routing, transport layer protocol, and application.

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Ns2 sources •

•

http://www.isi.edu/nsnam/ns/ – The source code and documentation is currently maintained by VINT project at ISI http://nsnam.isi.edu/nsnam/index.php/Main_Page – – –

• •

Sept 3, 2007: ns-2.32 released. Mar 10, 2007: ns-2.31 released. July 2, 2006: ns-3 project announced.

NS2 is a discrete event simulator targeted at networking research NS2 is an object oriented simulator, written in C++, with an OTcl interpreter as a frontend

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NS2 related Documentation • introductory: Marc Greis's tutorial • reference: Ns Manual (formerly called "ns Notes and Documentation") • ns by Example • Practical Programming in Tcl and Tk (http://www.beedub.com/book/) • http://hpds.ee.ncku.edu.tw/~smallko/ns2/ns2.htm

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NS2- Features • Collection of various protocols at multiple layers – – – – –

• • • • • •

tahoe, vegas, sack) MAC(802.11, 802.3, TDMA) Ad-hoc Routing (DSDV, DSR, AODV, TORA) Sensor Network (diffusion, gaf) Multicast protocols, Satellite protocols, and T(reno, many others

Traffic Models: CBR, VBR, Web, … Error Models: Uniform, Busty, … Misc: Radio Propagation, Mobility models, Energy Models, … Topology Generation tools (nsg2.1, ..) Visualization tools (NAM), Tracing Codes are contributed from multiple research communities – Good: Large set of simulation modules – Bad: Level of and documentation varies 04-Jul-14

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NS2 Chronicle • 1989: REAL by Keshav • 1995: ns by Floyd, McCanne at LBL • 1997: ns-2 by the VINT project (Virtual InterNetwork Testbed) at LBL, Xerox PARC, UCB, USC/ISI • Now: ns-2.35 maintained at USC/ISI • Also there is NS-3, but it has no backward compatibility with NS-2. 04-Jul-14

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NS2 Chronicle • REAL Simulator →NS (or NS1)→NS2→NS3. • NS-1 – LNBL Simulator tool – Developed by the network research group at the Lawrence – Berkeley National Laboratory (1989) – Derived from REAL Simulator – Simulation description language: TCL 04-Jul-14

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NS2 Chronicle • NS-2 – Object Oriented (OTcl instead of TCL) – Built in C++ and provides a simulation interface through OTcl – Developed by UC Berkeley – Difficult for the first time s • Very few friendly manuals. Ex: ns manual • Needs scripting language, queuing theory and modelling techniques knowledge • Complaint about inconsistent results • And BUGS!!!!

• But, large community 04-Jul-14

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NS3 • • • • • •

No backward compatibility with NS2 YANS (Yet Another Network Simulator)→NS-3 base NS-3.1 (2008), NS-3.11(2011), … Built in C++ and python Good for LTE and Wimax Simple to work with…..and suitable for dumping into and getting data from real-time devices. • No for some protocols which were ed in ns-2. • But, lesser community 04-Jul-14

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NS-2 Directory Structure ns-allinone Tcl8.0

TK8.0

OTcl

tclcl ...

tcl ex examples

test

ns-2

lib

nam-1

C++ code

mcast

...

validation tests OTcl code

simple.tcl 04-Jul-14

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NS-2 Environment Simulation Scenario

1

2

set ns_ [new Simulator]

Tcl Script

set node_(0) [$ns_ node] set node_(1) [$ns_ node]

C++ Implementation

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class MobileNode : public Node { friend class PositionHandler; public: MobileNode(); • • } udhayprakash.blogspot.in

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NS2 Architecture

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Why two languages? (Tcl & C++) • C++: Detailed protocol simulations require systems programming language – byte manipulation, packet processing, algorithm implementation – Run time speed is important – Turn around time (run simulation, find bug, fix bug, recompile, re-run) is slower

• Tcl: Simulation of slightly varying parameters or configurations – quickly exploring a number of scenarios – iteration time (change the model and re-run) is more important

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What is Tcl/Tk ? •It is a Scripting language to describe a high-level programming language with relatively transparent syntax •Tools Command Lanuage (TCL) –simple string based scripting language for controlling and extending applications.

–provides generic programming facilities such as variables, loops, and procedures. –Tcl syntax is very much similar to UNIX shell programming. •Tool kit (TK) – based on X-window system.

–provides facilities (widgets) for building interfaces.

•Tcl/Tk –Excellent tools for Rapid prototyping. –Tcl/Tk is interpreted rather than compiled. ( The interpreter is in !/opt/bin/wish ) –weakly typed language (strings and integer variables are interchangeable). 04-Jul-14

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Basic Tcl variables: set x 10 puts “x is $x”

procedures: proc pow {x n} { if {$n == 1} { return $x } set part [pow x [expr $n-1]] return [expr $x*$part] }

functions and expressions: set y [pow x 2] set y [expr x*x] control flow: if {$x > 0} { return $x } else { return [expr -$x] } while { $x > 0 } { puts $x incr x –1 } 04-Jul-14

Also lists, associative arrays, etc. => can use a real programming language to build network topologies, traffic models, etc.

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Basic oTcl Class Person # constructor: Person instproc init {age} { $self instvar age_ set age_ $age } # method: Person instproc greet {} { $self instvar age_ puts “$age_ years old: How are you doing?” } Person a 45 Kid b 15 a greet b greet04-Jul-14

# subclass: Class Kid -superclass Person Kid instproc greet {} { $self instvar age_ puts “$age_ years old kid: What’s up, dude?” } set a [new Person 45] set b [new Kid 15] $a greet $b greet # “new” in ns2 only

=> can easily make variations of existing things (T, T/Reno) udhayprakash.blogspot.in

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Split Object Model Split Object Model with shared class hierarchy –

•

TclCL provides ‘glue library’ to “easily” share functions, variables, etc – –

•

Control (OTcl) vs. Data (C++) OTcl into C++: command(), tcl.result() C++ into OTcl: tcl.eval()

Not all classes are mirrored exactly

OTcl OTcl script describing simulation

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C++

TclCL

•

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C++ and OTcl Linkage • Class Tcl: instance of OTcl interpreter Tcl& tcl = Tcl::instance(); tcl.evalc(“puts stdout hello world”); tcl.result() and tcl.error()

• Class TclObject and TclClass – Variable bindings bind(“rtt_”, &t_rtt_) – Invoking command method in shadow class $t advanceby 10

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Calling Otcl functions from C++ • OTcl Agent/T instproc advance {num} { set window_ [expr $window_ + $num] return $window_ }

• C++ Tcl& tcl = Tcl::instance(); char *result;

tcl.evalf(“%s advance %d”, name_, size); result = tcl.result(); wnd_ = atoi(result);

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EmbeddedTcl • How it works – tcl2c++: provided by TclCL, converts tcl scripts

into a C++ static character array – Makefile.in: tclsh8.0 bin/tcl-expand.tcl tcl/lib/ns-lib.tcl | tcl2c++ et_ns_lib > gen/ns_tcl.cc

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C++ and OTcl Separation • “data” / control separation – C++ for “data”: • per packet processing, core of ns • fast to run, detailed, complete control

– OTcl for control: • • • •

Simulation scenario configurations Periodic or triggered action Manipulating existing C++ objects fast to write and change

+ running vs. writing speed – Learning and debugging (two languages) 04-Jul-14

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Object Granularity Tips • Functionality – Per-packet processing  C++ – Hooks, frequently changing code  OTcl

• Data management – Complex/large data structure  C++ – One-time configuration variables  OTcl

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Ns2 Installation Procedure • Linux Installation (preferred): – Go to udhayprakash.blogspot.in – Search for ns2 installation procedure – Follow it …..!

• Windows Installation – Go to http://nsnam.isi.edu/nsnam/index.php/Running_Ns _and_Nam_Under_Windows_9x/2000/XP_Using_ Cygwin 04-Jul-14

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Where to find…/ns-2/tcl/lib • ns-lib.tcl: – The simulator class and most of its member function definitions

• ns-default.tcl: – The default values for configurable parameters

• ns-packet.tcl: – The packet header format initialization implementation

• other OTcl files: – implementation of compound network objects or the front end (control part) of network objects

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SESSION -2 Working with Ns2

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A Simple Topology

Application

n0

n1

Agent

Agent

0

0 1 0

0 1

head_

enqT_

queue_

drophead_

deqT_

link_

ttl_

rcvT_

drpT_

Link n1 – n0

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N1

N2 Node

Node

Application

Classifier

Port

Local

Agent

Classifier

Classifier

Classifier

Local

Port

Agent Application

Addr

Addr Link Enq Trace

Queue

Link

Drop head

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Deq Trace

Delay

TTL

Rcv Trace

Drp Trace

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Using ns Problem

Result analysis

Simulation model

Modify ns

Setup/run simulation with ns 04-Jul-14

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NS-2 Generic Script Structure set ns [new Simulator] # [Turn on tracing] # [Turn on visualizer visualizer] ] # Create topology # Setup packet loss, link dynamics # Create routing agents # Create: # - multicast groups # - protocol agents # - application and/or setup traffic sources # PostPost-processing procs # Start simulation

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Event Scheduler Creation • Event is a packet ID that is unique for a packet, which constitutes: – Scheduled time – The pointer to an object that handles the event • An event scheduler – Keeps track of simulation time – Fires all the events in the event queue

• Create event scheduler: set ns [new simulator] • Schedule an event: $ns at <event> – Event is any legitimate ns/tcl function – $ns at 5.0 “finish”

• Start scheduler – $ns run 04-Jul-14

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Tracing

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Tracing • Packet tracing and event tracing – Objects that are inserted between nodes – Insert from OTcl using trace{} method • $ns trace-all $file, or • [$ns link $n0 $n1] trace $file

• Monitoring – Record counters of interest for all packets or on a per-flow basis

• …or roll your own 04-Jul-14

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Tracing • ns and nam trace file formats – ns also s show_thdr_ variable controlling display of T flags

• ns format op

ts

prevhop

nexthop

type

size

flags

flowid

src

dst

seqno

pktid

+

1.102

0

1

t

40

––––––

0

0.0

1.0

1

1

• Enque [+], dequeue [-], receive [r], drop [d] • Types are • Flags are – ECN-CE [E], -ECT [N], -CE [C], -CWR [A]; plus – priority [P] and T fast start [F] 04-Jul-14

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Visualization (nam) set nf [open out.nam w] $ns namtrace-all $nf Proc finish {} { global ns nf close $nf exec nam out.nam & exit 0 }

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Topology Creation

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Sending Data

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Sending Data

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Creating T Connections • Create T agent and attach it to the node set t0 [new Agent/T] $ns attach-agent $n0 $t0

• Create a Null Agent and attach it to the node Set null0 [new Agent/TSink] $ns attach-agent $n1 $null0

• Connect the agents $ns connect $t0 $null0

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Traffic on top of T • FTP – set ftp [new Application/FTP] – $ftp attach-agent $t0

• Telnet – Set telnet [new Application/Telnet] – $telnet attach-agent $t0

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NS2 pre- and post processing • pre-processing: – traffic and topology generators – NSG 2.1 (for more details, go to udhayprakash.blogspot.in ) – tclTutor

• post-processing: – simple trace analysis, often in Awk, Perl, or Tcl. – Awk scripting is preferred.

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Summary • Simulators help in easy verification of protocols in less time, money. • NS2 offers for simulating a variety of protocols suites and scenarios • Front end is oTCL, back end is C++ • NS2 is on-going effort of research and development.

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Reference 1) 2) 3) 4) 5) 6) 7) 8) 9)

ns2 website: http://www.isi.edu/nsnam/ns Marc Greis' tutorial Jae Chung tutorial Ns manual Tcl/Tk – http://www.tcl.tk/software/tcltk/ Nsnam web pages – http://www.isi.edu/nsnam/ NS by example – http://nile.wpi.edu/NS/ Tutorial – Marc Greis's tutorial Discrete-event simulation software – http://www.topology.org/soft/sim.html 10) Introduction to NS2(PPT), Prepared by Changyong Jung 04-Jul-14

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